A habitable zone, shown here in green, is defined as the region around a star where liquid water – an essential ingredient for life as we know it – might exist. But can life exist outside this zone? Here, a hypothetical exoplanet is depicted moving through its sun’s habitable zone and then further out into a long, cold winter. At the far part of its orbit, water will freeze at its surface. But could life continue if it hibernated beneath the surface? Image credit: NASA/JPL-Caltech Image credit: NASA/JPL-Caltech

EARTHSKY // BLOGS // SPACE Deborah Byrd JAN 07, 2013

Habitable zone around stars might be larger than we think

Could life survive on a world whose orbit around a distant sun was extremely oblong and eccentric? Such a world would have periods of extreme heat and cold.

Life is various, and it’s inclusive. It includes all sorts of creatures, habitats, ways of surviving, ways of being that we humans can’t really imagine unless we go out, search and make surprising discoveries. For example, who would have imagined prior to 1977 – when Jack Corliss and colleagues unexpectedly discovered communities of living creatures (giant tube woms, clams, shrimp) in and around hydrothermal vents – that life could exist in such an extremely hot environment as an undersea volcano? And yet life does exist in such places. Now astronomers who contemplate life in even more exotic places – planets orbiting distant suns – are wondering if they should expand their thinking about what’s known as the habitable zone around stars.